The Use of Trilostane for the Treatment of Alopecia X in Alaskan Malamutes

Canine noninflammatory alopecia: An approach to its classification and a diagnostic aid

Noninflammatory alopecia is common in dogs and is a frequent cause to consult a veterinarian. It is also a common reason to take biopsies. Noninflammatory alopecia can be attributed to a decreased formation or cytodifferentiation of the hair follicle or the hair shaft in utero, resulting in congenital alopecia. Congenital alopecia often has a hereditary cause, and examples of such disorders are ectodermal dysplasias associated with gene variants of the ectodysplasin A gene. Noninflammatory alopecia may also be caused by impaired postnatal regeneration of hair follicles or shafts. Such disorders may have a clear breed predilection, and alopecia starts early in life. A hereditary background is suspected in those cases but has not been proven. They are referred to as follicular dysplasia although some of these disorders present histologically like a hair cycle disturbance. Late-onset alopecia is usually acquired and may be associated with endocrinopathies. Other possible causes are impaired vascular perfusion or stress. As the hair follicle has limited possible responses to altered regulation, and histopathology may change during the course of a disease, a detailed clinical history, thorough clinical examination including blood work, appropriate biopsy site selection, and detailed histological findings need to be combined to achieve a final diagnosis. This review aims to provide an overview about the known noninflammatory alopecic disorders in dogs. As the pathogenesis of most disorders is unknown, some statements are based on comparative aspects or reflect the authors' opinion.

Deslorelin Implant Treatment for Hair Cycle Arrest (Alopecia X) in Two Intact Male Keeshonden

Alopecia in dogs occurs secondary to a variety of underlying inflammatory and noninflammatory conditions. Hair cycle arrest (alopecia X) is a noninflammatory alopecia that is frustrating to diagnose and treat due to lack of understanding of disease pathogenesis. A variety of therapies for hair cycle arrest have been described with inconsistent efficacy in different dog breeds and sexes; no definitive treatment is available. This report describes the use of a deslorelin acetate implant in two sexually intact adult male keeshonden, both diagnosed with hair cycle arrest. The dogs had progressive alopecia of the trunk that spared the head and distal limbs present for at least 2 yr. Diagnosis of hair cycle arrest was made based on clinical features, dermatohistopathology, and lack of systemic abnormalities. Treatment with a single subcutaneous 4.7 mg deslorelin acetate implant resulted in profuse hair regrowth within 3.5 mo that endured for at least 14 mo. Deslorelin implantation is a management option that is safe, affordable, and appears effective for sexually intact male keeshonden with hair cycle arrest.

Canine noninflammatory alopecia: a comprehensive evaluation of common and distinguishing histological characteristics

BACKGROUND

Noninflammatory alopecia is a frequent problem in dogs, and the pathogenesis is still unclear.

OBJECTIVE

The objective of this study was a comparative histological description of skin biopsies from dogs with different alopecic disorders and control dogs matched for coat type, season and disease duration.

ANIMALS

Twenty-one cases of alopecia X in plush-coated dogs, 12 cases of recurrent flank alopecia, three cases of hyperestrogenism, 15 cases of hyperadrenocorticism, 12 cases of hypothyroidism and 12 cases of primary alopecic disorders of unknown cause were evaluated. The controls were biopsies from 38 dogs of different coat types.

METHODS

We evaluated five serial sections of each biopsy histologically and immunohistologically to compare the histological findings within the disease groups and with the control.

RESULTS

All the dogs with hair cycle disorders had a significant increase in the number of hairless hair follicles, which we assigned to kenogen. In addition, dogs with alopecia X had the lowest percentage of anagen follicles and the highest percentage of telogen follicles.

CONCLUSIONS

The marked increase in kenogen follicles is a strong indication that the induction of the new anagen phase is impaired in hair cycle disorders. The findings in dogs with alopecia X further suggest that premature catagen is also involved in the pathogenesis. Further work to investigate the stem cell compartment and possible initiating factors for the different cycle phases is required to elucidate the exact pathogenesis.

Trilostane in dogs

Over the last 10 years, trilostane, a competitive inhibitor of steroid synthesis, is being widely used for the treatment of canine hyperadrenocorticism. Trilostane causes a significant but reversible decrease in cortisol production and a concomitant improvement in clinical signs in most dogs with this common condition. Side effects, though infrequent, can be serious: dogs treated with this drug require regular monitoring. This review summarizes current knowledge of the use of this drug with particular emphasis on its efficacy, safety, adverse reactions, and effects on endocrine parameters. Brief mention is made of its other uses in dogs and other species.

Hyperadrenocorticism associated with sex steroid excess

Diagnosis of sex steroid excess or hyperadrenocorticism in dogs may be challenging. Unlike Cushing's disease, sex steroid excess may have a multitude of manifestations that differ from standard hyperadrenocorticism. In particular, the clinical scenario of a dog with sex steroid imbalance involves one of three systems: dermatologic, reproductive, or hepatic. The history of a dog with hyperadrenocorticism manifesting as sex steroid imbalance often lacks the classical clinical signs of polydipsia and polyuria. Dogs with sex steroid imbalance will often be of specific breeds such as miniature poodles and exhibit trunkal hair loss as the only sign. There is often involvement of the reproductive system, manifested as the growth of perianal adenomas in neutered male or female dogs. The most common laboratory findings consist of elevations in serum alkaline phosphatase and serum alanine transferase. The following article reviews the etiology, common signalment, clinical signs, and laboratory findings associated with atypical hyperadrenocorticism caused by sex steroid imbalance and then explores the medical, surgical, and radiation treatment options.